1. Field of the Invention
The present invention relates to a polyphenylene ether resin composition which has good processability and can provide a molded article with good impact resistance. More particularly, the present invention relates to a polyphenylene ether resin composition which comprises a polyphenylene ether resin, an unsaturated nitrile compound/vinyl aromatic compound/diene rubber resin, one or two kinds of graft copolymers having specific compositions and optionally an aromatic vinyl compound/diene rubber resin and has good processability and can provide a molded article with good impact resistance.
2. Description of the Related Art
Polyphenylene ether resin has good heat and impact resistances, but it is difficult to mold and process said resin alone. Thus, there was proposed a resin composition comprising a polyphenylene ether resin and an aromatic vinyl resin which has improved processability (cf. U.S. Pat. No. 3,383,435).
Although the processability of the polyphenylene ether resin composition is improved, the inherent properties of the polyphenylene ether resin composition such as heat and impact resistances are substantially impaired.
As described in U.S. Pat. No. 3,383,435, known aromatic vinyl resins include polystyrene, rubber-modified polystyrene (HIPS), unsaturated nitrile compound/aromatic vinyl compound/diene rubber resins (ABS resins) and the like. Among the aromatic resins, the ABS resins comprising the unsaturated nitrile compound and the diene rubber have the best impact and solvent resistances.
However, since the ABS resins have poor compatibility with the polyphenylene ether resins, a resin composition of the ABS resin and the polyphenylene ether resin has significantly impaired mechanical properties such as impact resistance although the processability of the composition is improved as in case of the resin composition of polystyrene and the polyphenylene ether resin.
In fact, no resin composition comprising the ABS resin and the polyphenylene ether resin has been practically used although the resin composition comprising the polyphenylene ether resin and polystyrene or HIPS is practically used.
Studies on improvement of the compatibility between the polyphenylene ether resin and the ABS resin have been made and concrete improving techniques are disclosed in U.S. Pat. Nos. 4,360,618 and 4,405,753. In the former U.S. Pat. Nos., the ABS resins are limited to those containing acrylonitrile in low content, namely 2 to 8 % by weight based on the finding that acrylonitrile in the ABS resins is a cause for the poor compatibility. In the latter U.S. patent, the ABS resins are limited to those having a low acrylonitrile content, namely 2 to 15 % by weight, and an ethylenically unsaturated dicarboxylic anhydride/aromatic vinyl compound resin is introduced.
Although the compatibility is improved by lowering the acrylonitrile content in the ABS resins as described in U.S. Pat. Nos. 4,360,618 and 4,405,753, it is impossible to use general ABS resins which contain acrylonitrile in an amount of 20 to 30 % by weight. In addition, the resin composition comprising the ABS resin having the low acrylonitrile content and the polyphenylene ether resin has still unsatisfactory impact resistance.